Abstracts

Rationale: Driving safety is a critical concern among patients with epilepsy. Permission to drive is usually given if overt seizures are controlled. However previous studies suggest that subclinical epileptiform discharges (SEDs) might exert an additional and independent subtle effect on transient cognitive processes (alertness, mental speed etc), and it is unclear whether such SEDs might pose a threat to driving safety, particularly when SEDs are of sustained duration. Methods: The present study focused on the effects of sustained >1 s duration SEDs on driving safety, in comparison to clinically overt seizures. A computer-based video driving simulator was prospectively applied for inpatients with epilepsy who underwent continuous video-electroencephalography (VEEG) monitoring while admitted to our epilepsy center. EEG recordings of clinical seizures, SEDs, video/behavioral recordings and synchronized driving data were extracted and analyzed. Clinical relevance with regard to driving behavior during clinical seizures and SEDs was evaluated by using crashing the car as a terminal impairment criterion. Results: 30 clinical seizures and over 100 SEDs with duration >1s were found. By comparing the baseline of driving performance for each participant with seizure or SED epochs, we determined changes in car velocity, steering wheel movement, accelerator position, and crash rates during SEDs compared to baseline driving performance on the same track segments. We found that clinical seizures with impaired consciousness were inevitably (8/8 seizures) associated with impaired driving and crash. There was also a trend for seizures with more severe motor impairment (with or without impaired consciousness) to cause unsafe driving. SEDs were overall less commonly associated with crashes. By analysis of SED characteristics such as morphology, and localization (temporal, extemporal, generalized) there seems to be a trend that longer lasting generalized SEDs were more likely associated with a crash. Ongoing analyses are investigating other SED characteristics possibly associated with subtle driving impairment. Conclusions: Whereas clinical seizures with overt impaired consciousness or abnormal motor activity were often clearly associated with driving impairment, the effects of SEDs was less clear and will require further investigation. There appeared to be a trend for greater impairment and more frequent crashes with SEDs of longer duration, however additional quantitative analysis of driving performance metrics will be needed to determine if more subtle driving impairment can be associated with specific SED characteristics.